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What is the volatile keyword useful for?
... volatile:
public class Singleton {
private static volatile Singleton _instance; // volatile variable
public static Singleton getInstance() {
if (_instance == null) {
synchronized (Singleton.class) {
if (_instance == null)
_instance = ...
Specifying rails version to use when creating a new application
...option to create a new application using an older version of Rails.
rails _2.1.0_ new myapp
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Getting SyntaxError for print with keyword argument end=' '
I have this python script where I need to run gdal_retile.py ,
but I get an exception on this line:
14 Answers
...
Get IP address of visitors using Flask for Python
...est object and then get from this same Request object, the attribute remote_addr.
Code example
from flask import request
from flask import jsonify
@app.route("/get_my_ip", methods=["GET"])
def get_my_ip():
return jsonify({'ip': request.remote_addr}), 200
For more information see the Werkzeu...
Converting between datetime, Timestamp and datetime64
...amp(ts)
datetime.datetime(2012, 12, 4, 19, 51, 25, 362455)
>>> np.__version__
'1.8.0.dev-7b75899'
The above example assumes that a naive datetime object is interpreted by np.datetime64 as time in UTC.
To convert datetime to np.datetime64 and back (numpy-1.6):
>>> np.datetime6...
Converting camel case to underscore case in ruby
...ef underscore
self.gsub(/::/, '/').
gsub(/([A-Z]+)([A-Z][a-z])/,'\1_\2').
gsub(/([a-z\d])([A-Z])/,'\1_\2').
tr("-", "_").
downcase
end
end
Then you can do fun stuff:
"CamelCase".underscore
=> "camel_case"
...
Getting MAC Address
...inding function into your own code easily:
from uuid import getnode as get_mac
mac = get_mac()
The return value is the mac address as 48 bit integer.
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Most efficient way to remove special characters from string
...ed characters are A-Z (uppercase or lowercase), numbers (0-9), underscore (_), or the dot sign (.).
24 Answers
...
Create a “with” block on several context managers? [duplicate]
...nd 3.1 and above, you can write:
with A() as X, B() as Y, C() as Z:
do_something()
This is normally the best method to use, but if you have an unknown-length list of context managers you'll need one of the below methods.
In Python 3.3, you can enter an unknown-length list of context manage...
Cosine Similarity between 2 Number Lists
...sed on numpy only
from numpy import dot
from numpy.linalg import norm
cos_sim = dot(a, b)/(norm(a)*norm(b))
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